Record carrier

ABSTRACT

The invention relates to a record carrier ( 1 ) comprising an area for storing data, the record carrier adhering to a pre-defined, standardized condition with respect to a physical parameter. The record carrier comprises parameter information on the physical parameter, which parameter information is of a higher precision than the precision of the physical parameter mentioned in the pre-defined, standardized condition. Using this high precision parameter information, it is possible to derive the exact position of a visible image pixel data making up a label. This parameter information thus enables a recorder to write a visible label on the record carrier according to the invention.

The invention relates to a record carrier comprising an area for storingdata, the area comprising a pattern of tracks for storing the data inthe form of marks, the record carrier adhering to a pre-defined,standardized condition with respect to a physical parameter.

A record carrier of this type is well known, for example from thestandardized rewritable and/or recordable optical record carriers CD-R,CD-RW, DVD+R or DVD+RW, or the read-only CD-Audio disc. The data on thistype of record carriers is written in a continuous clock-wise spiralfrom the inner radius to the outside radius. The documents in whichthese standardized optical record carriers are described (so-calledstandard specifications) specify conditions with respect to physicalparameters these record carriers must adhere to, like for example theinner radius, the track pitch and the channel bit length The nominalvalue of these parameters is sometimes also stored on the recordcarrier, for example in a lead-in area.

It is an object of the invention to realize a record carrier thatenables a standard drive to more easily read data from the recordcarrier or write data on the record carrier, for example for writing avisible label on the record carrier.

According to the invention, this object is achieved by a record carrierthat is characterized in that the record carrier comprises parameterinformation on the physical parameter, which parameter information is ofa higher precision than the precision of the physical parametermentioned in the pre-defined, standardized condition.

In order to be able to identify and find a particular record carrier, itis necessary that the user of these record carriers consistently labelshis otherwise anonymous record carriers before or after recording. Ingeneral, the average user does not do this very diligently. In order toovercome this problem, it would be convenient if a visible label can bewritten during the recording of the information on the record carriers.However, such a standardized record carrier has as a drawback that aknown standard drive for recording data on such a record carrier cannotwrite a visible label on it. In order to be able to write a label on arecord carrier, it is crucial to know exactly where the written visibleimage pixels data making up the label end up on the record carrier area,as the pixels must be written in a two-dimensionally co-ordinated way.The inventors have recognized, inter alia, that due to fact that thestandard specifications for read-only, recordable and rewritable mediaonly specify this physical parameter to a certain precision, smallerrors in this parameter will cause a significant distortion in thelabel written on the record carrier. An apparent insignificantinaccuracy in such a physical parameter will thus have largeconsequences for the label writing process. The inventors indeed foundthat due to this, a label in the form of a block got warped into ahardly recognizable spiral pattern. From this the inventors have drawnthe conclusion that a more accurate indication of certain physicalparameters was needed. These physical parameters can be used by astandard drive for determining the entire mapping of the channel bitsover the record carrier and thus also for determining where the writtenvisible image pixels data making up the label end up on the recordcarrier.

A preferred embodiment of the record carrier according to the inventionis characterized in that the parameter information is to be used forassisting writing a visible label on the record carrier.

It must be noted that writing a visible label on the record carrieraccording to the invention is only one possible application. Theparameter information can also be used for fast retrieval of the datastored on the record carrier or for additional certainty on the exactposition on which data is to be written, e.g. in defect managementschemes.

A further embodiment of the record carrier according to the invention ischaracterized in that the physical parameter is the track pitch of therecord carrier. A further embodiment is characterized in that theaverage track pitch, according to the pre-defined, standardizedcondition with respect to the track pitch, when expressed in micrometer,is expressed in two decimals, and that the information on the trackpitch stored on the record carrier, when expressed in micrometer, isindicated in at least three decimals. Another further embodimentcharacterized in that the record carrier is a DVD−RW disc or a DVD+RWdisc, and the average track pitch is 0.74 μm. These embodiments have asan important advantage that by storing on the record carrier the trackpitch in a highly accurate manner, at least more accurate than therequirements of the track pitch imposed on the record carrier, it ispossible to accurately calculate the tangential position on the recordcarrier where the label data end up on the record carrier. For example,according to the DVD−RW and DVD+RW specification, the average trackpitch is indicated in two decimals, 0.74 μm. On the record carrieraccording to the invention can be stored a more accurate average trackpitch, for example 0.737 μm. As another example of this higher accuracy:the inventors have measured for a specific batch of DVD−RW discs a trackpitch of 0.7443251 μm.

A further embodiment of the record carrier according to the invention ischaracterized in that the physical parameter is the channel bit length.A further embodiment is characterized in that the average channel bitlength, according to the pre-defined, standardized condition withrespect to the channel bit length, when expressed in nanometer, isexpressed in one decimal, and that the information on the channel bitlength stored on the record carrier, when expressed in nanometer, isindicated in at least two decimals. A further embodiment ischaracterized in that the record carrier is a DVD−RW disc or a DVD+RWdisc, and the average channel bit length is 133,3 nm. As an example ofthis higher accuracy: the inventors have measured for a specific batchof DVD-RW discs an average channel bit length of 134.11443 nm. Theseembodiments have as an important additional advantage that if thechannel bit length is known with a high precision, rotational distortionof the label to be written can be prevented. It can be understood thatdue to a small inaccuracy in the channel bit length, it will become verydifficult to calculate the exact radial position of a certain labelpixel.

A further embodiment of the record carrier according to the invention ischaracterized in that the physical parameter is the inner radius of therecord carrier. A further embodiment is characterized in that the innerradius, according to the pre-defined, standardized condition withrespect to the inner radius, when expressed in millimeters, is expressedin one decimal, and that the information on the inner radius stored onthe record carrier, when expressed in millimeters, is indicated in atleast two decimals. A further embodiment is characterized in that therecord carrier is a DVD−RW disc or a DVD+RW disc, and the inner radiusis 24.0 mm. These embodiments have as an important additional advantagethat knowledge of exact position of the inner radius will enabledetermining the tangential position of a certain label pixel in anaccurate manner.

The high precision parameter information can be obtained in manydifferent ways. If the mastering process can be very properlycontrolled, it is possible to store the parameter information on therecord carrier during mastering. In a further embodiment, the parameterinformation is stored in a wobble. A wobble is a continuous sinusoidaldeviation of the track from the average centerline. A record carriercomprising such a sinusoidal deviation is for example known from U.S.Pat. No. 4,972,401 (=PHN 9666), which document is hereby incorporated byreference. In another embodiment, the parameter information is stored inpits embossed on the lands, so-called pre-pits. These embodiments haveas an advantage that the parameter information can be incorporated intoalready existing storage techniques. The use of a wobble for storingdata is for example used in the DVD+RW disc and the use of pre-pits forstoring data is for example used in the DVD−RW disc. It is also possibleto store the parameter information after mastering of the recordcarrier. When storing the parameter information in a wobble or inpre-pits, it is advantageous when, for this use, a special area on therecord carrier is defined. In this way, it is possible to reliablyretrieve the parameter information, even without having exact knowledgeon the physical parameters of the record carrier itself.

In another embodiment of the record carrier according to the invention,the parameter information is stored in a pre-defined data field on therecord carrier. This embodiment has as an advantage that the parameterinformation can be reliably retrieved. Preferably, this pre-defined datafield is situated in the lead-in of the record carrier, e.g. in the DiscManufacturing Information field in the lead-in.

In another embodiment, the record carrier according to the inventioncomprises a further area comprising an integrated circuit, the parameterinformation being stored in the integrated circuit. A record carrier onwhich an integrated circuit is present is for example known fromInternational application with international publication number WO02/17316 A1 (=PH-NL010233), which document is hereby incorporated byreference. This embodiment has as an advantage that the parameterinformation can be stored after mastering of the record carrier. Thishigh precision parameter information can be stored on the record carriereven if the mastering process cannot be controlled very accurately, asthe value of the physical parameter is determined by measuring theproduced record carrier and the corresponding parameter information isafterwards stored in the integrated circuit. The embodiment further hasas an advantage that the parameter information present in an integratedcircuit can be read out even before the player is capable of reading outthe data present in the data area.

These and other aspects of the invention are apparent from and will beelucidated with reference to the embodiments described hereinafter.

In the drawings:

FIG. 1 shows diagrammatically an embodiment of the record carrieraccording to the invention,

FIG. 2 shows a table comprising parameter tolerances for a DVD−RW disc,

FIG. 3 shows a table comprising parameter tolerances for a DVD+RW disc,

FIG. 4 shows two embodiments of the record carrier according to theinvention in which the parameter information is stored in a physicaldeviation of the track,

FIG. 5 shows an embodiment of the record carrier according to theinvention comprising an integrated circuit in which the parameterinformation is stored,

FIG. 6 shows a possible application of the visible label, which can bewritten, on the record carrier according to the invention.

FIG. 1 shows a recordable record carrier 1, for example a DVD+RW likedisc, having a central aperture 2 and data area 3. The data to be storedon recordable optical media like CD-R or DVD−RW is written in acontinuous clock-wise spiral from the inner radius to the outside. Thefirst part of the data area is reserved as lead-in area with variousspecial purposes. After that comes the usable data area, which in turnis followed by a lead-out area. When recording a record carrier, someparts of the lead-in area are updated, the data area is written, andafter the last valid data area a lead-out area is written. As mentionedabove, in order to be able to write a visible image on the recordcarrier, it is crucial to know exactly where written data end up on thedata area 3.

In order to know where the channel bits end-up on the data area 3, it isnecessary to analyze the way a standardized record carrier is defined.Recordable and rewritable media are mastered with a groove and sectoraddress indication (e.g. in the rewritable DVD+RW disc a wobbling grooveis used for sector address indication; in the recordable DVD−R discpre-pit information relating to the sector address is present in theland). The standard specification for these media generally prescribesthe physical layout in terms of inner radius R₀, track pitch D_(tp) andchannel bit length L_(cb), but does not define the details of the discmastering. The inner radius R₀ is the radius on a record carrier atwhich the information area begins. The data area normally comprisesthree areas, the lead-in area, a data recording area and a lead-outarea. The track pitch D_(tp) is the distance between adjacent tracksmeasured in the radial direction. The channel bit length L_(cb) is theunit length T of a channel bit. For example in DVD, the minimumrecording pit length is equal to three times the channel bit length, 3T,and the maximum recording pit length is equal to eleven times thechannel bit length, 11T. Given these parameters, however, it is inprinciple possible to figure out the entire mapping of the channel bitsover the record carrier, if it is assumed that the data density isexactly uniform over the disc, i.e. a spiral with perfectly constanttrack pitch D_(tp) and channel bit length L_(cb), and that startsexactly at inner radius R₀. For a spiral, the radius r grows with asingle track pitch D_(tp) for every revolution, so r simply dependslinearly on the cumulative angle Φ:r(Φ)=R ₀ +D _(tp)Φ/2π

By integrating along the track length, we find the relation between bitstring position l and the cumulative angle Φ:l L _(cb) =∫r(Φ)dΦ=∫(R ₀ +D _(tp)Φ/2π)dΦ=R ₀ D _(tp)Φ²/4πSolving for Φ yields:Φ(l)=2π{√(l L _(cb) D _(tp) /π+R ₀ ²)−R ₀ }/D _(tp)andr(l)=√(l L _(cb) D _(tp) /π+R ₀ ²)

The problem is that the inner radius R₀, track pitch D_(tp) and channelbit length L_(cb) are known only to a certain precision. This isindicated in FIGS. 2 and 3, which shows a table comprising parametertolerances for a DVD−RW disc and for a DVD+RW disc. For the radius r(l)this is not always a problem, as the specified precision is sufficientfor most practical purposes. Small relative errors in  (l), however,give rise to disastrous errors in the reduced angle φ:φ(l)=Φ(l) mod 2π.

E.g. a DVD disc uses more than 40.000 revolutions from the inner radiusto the outer radius. Hence a relative error of 1% in Φ(l) corresponds tomore than 40000% error in φ(l): a 1% error in Φ(l) causes the labelimage to be rotationally warped over more than 400 revolutions! Theproblem is of course that a tiny miscalculation of the data length perrevolution accumulates to a huge error after 40000 revolutions. Inexperiments, the inventors found indeed errors of this magnitude: anominal block pattern in the radius r(l) looks perfectly all right, buta nominal 180° block pattern in the reduced angle Φ(l) gets warped intoa hardly recognizable spiral pattern. From this the inventors drew theconclusion that more accurate information on the physical parametersused for determining the position of the data pixels is needed.

Closer inspection of the equation for Φ(l) shows that the threeconstants R₀, D_(tp) and L_(cb) result in only two media master specificparameters A and B:Φ(l)=·(A l+B ²)−BwithA=4π·L _(cb) /D _(tp)B=2πR ₀ /D _(tp)A more intuitive explanation for a two parameter description is that thelinear spiral can be defined by the amount of data that is written inthe first revolution of the track, and the fixed growth of that amountper revolution (this leaves the scale of the spiral as a thirdparameter, but the scale does not affect the rotational warp andtherefore does not have to be known at great precision). This simple twoparameter problem can give rise to rather spectacular but undesirablewarp patterns when the parameters are slightly off.

Experiments showed that several iterations in the visual calibrationprocedure are needed to achieve the required sub-ppm precision in A andB for less than 1 nm distortion in the visible label. It was found thatthe result of the two parameter iterative fit procedure is not onlyreproducible within one disc, but even between several rewritable discsbought in a single pack. Apparently discs from a single batch tend tocome from a single master template.

FIG. 4 shows two embodiments of the record carrier according to theinvention in which the parameter information is stored in a physicaldeviation of the track. In this Figure, an enlargement of box 4indicated in FIG. 1, two possible implementations of such a physicaldeviation are depicted. In these implementations the parameterinformation is stored in the lead-in of the record carrier. Track 4.1shows a track in which the parameter information is stored as a widthvariation of the track. This variation has a certain length, indicatedwith the reference number 5. The parameter information can be read outfrom the record carrier using the tracking signals available in astandard device for reading out record carriers, e.g. a CD or DVDplayer. Track 4.2 shows a track in which the parameter information isstored as in the form of a deviation of the track from the averagecenterline 6. Such a deviating track, which is generally called awobble, is used in different standardized optical record carriers, likee.g. the CD-R disc and the DVD+RW disc. Additional information can befound in the already mentioned U.S. Pat. No. 4,972,401 (=PHN 9666).

FIG. 5 shows an embodiment of the record carrier according to theinvention comprising an integrated circuit 7 in which the parameterinformation is stored. The parameter information can be stored in theintegrated circuit during or after mastering. Additional information onrecord carriers comprising integrated circuits can be found in thealready mentioned International application with internationalpublication number WO 02/17316 A1 (=PH-NL010233) and in the documentsmentioned therein.

The label to be written on the record carrier can be used for all kindsof different applications. The most obvious application is to use thedisc label technique as a means of identification of recorded media forthe end-user. Another application resides in the realm of copyprotection. The label can than serve as a hard-to-copy visual watermarkof the content.

The disc label can be written on different places of the disc. It canfor example be placed after the regular data, either inside or outsidethe lead-out area, but it can also be positioned in an inner diameterring, or in rings between the normal data. It is also possible to insertthe label among the regular data area. In general, the label can bewritten on any possible place on the read-out side of the disc.

The label can be written on the record carrier in many different ways.International application with international publication number WO02/41316 A1 (=PH-NL010604), which document is hereby incorporated byreference, discloses a record carrier with a watermark which is storedon the record carrier by using a certain freedom in the channel code forintroducing a predefined run length distribution in the marks to bestored on the record carrier. It is also possible not to store the labelin the data area of the record carrier, but to use a predefinednon-information area of the record carrier. In such an area marks withrepeated minimum or maximum runlengths are written for creating therequired visual effect. This is for example disclosed in U.S. Pat. No.5,608,717, which document is hereby incorporated by reference.

With reference to FIG. 6, an example of the procedure for writing alabel on a record carrier according to the invention is explained. Inthis example, the following steps are taken:

1. Select the label to be written on the record carrier (e.g. the labelon FIG. 6A),

2. Read out the parameter information relating to the required physicalparameter(s) from the record carrier,

3. Start with the first data byte to be written on the disc,

4. Derive the polar coordinates (r, φ) of that byte using the physicalparameter information (see FIG. 6B),

5. Convert to the corresponding pixel coordinates in the label image,

6. Determine the corresponding pixel value in the label image,

7. Select the required channel symbol,

8. Repeat from 4 for the next data bytes to be written on the disc.

This is a computationally very expensive approach. By using the repeatednature of the pixel values at certain positions, the computational timerequired can be reduced. To this end, the edges of the label patternmust first be found, e.g. to find the next label pixel that has adifferent pixel value.

The inventors have found out that many DVD discs are mastered with suchstability that the use of parameter information relating to two physicalparameters can be sufficient for creating a visual label with negligibledistortions. However, the use of parameter information relating to onlyone physical parameter can be sufficient for certain applications. Forother applications, parameter information relating to more than twoparameters might be required.

Although the invention has been elucidated with reference to theembodiments described above, it will be evident that other embodimentsmay be alternatively used to achieve the same object. The scope of theinvention is therefore not limited to the embodiments described above,but can be applied to all kinds of record carriers, read-only as well asrecordable/rewritable ones, adhering to certain, pre-defined physicalparameters.

It must also be noted that the invention is not limited to the storageof parameter information relating to one physical parameter. In order tofurther optimize the writing process of the label, information relatingto different physical parameters can be combined. The invention is alsonot limited to certain physical parameters. All physical parameterswhich can be used for determining the position of a certain bit on therecord carrier belong to the scope of the claims. This includes, besidesthe physical parameters already mentioned, the exact amount of data perrevolution or the number of revolutions on a disc. The invention is alsonot limited to certain methods for writing a label on a record carrier.All methods which use a physical parameter for writing a label on theread-out side of a record carrier can be used for writing such a labelon the record carrier according to the invention. The invention is alsonot limited to a certain use of the parameter information present on therecord carrier according to the invention. Although writing of a visiblelabel is a preferred application of this parameter information, allkinds of uses relating to reading and writing of data can be appliedusing this parameter information.

It must further be noted that the term “comprises/comprising” when usedin this specification, including the claims, is taken to specify thepresence of stated features, integers, steps or components, but does notexclude the presence or addition of one or more other features,integers, steps, components or groups thereof. It must also be notedthat the word “a” or “an” preceding an element in a claim does notexclude the presence of a plurality of such elements. Moreover, anyreference signs do not limit the scope of the claims; the invention canbe implemented by means of both hardware and software, and several“means” may be represented by the same item of hardware. Furthermore,the invention resides in each and every novel feature or combination offeatures.

The invention can be summarized as follows: the invention relates to arecord carrier comprising an area for storing data, the record carrieradhering to a pre-defined, standardized condition with respect to aphysical parameter. The record carrier comprises parameter informationon the physical parameter, which parameter information is of a higherprecision than the precision of the physical parameter mentioned in thepre-defined, standardized condition. Using this high precision parameterinformation, it is possible to derive the exact position of a visibleimage pixel data making up a label. This parameter information thusenables a recorder to write a visible label on the record carrieraccording to the invention.

1. A record carrier (1) comprising an area for storing data, the areacomprising a pattern of tracks (3) for storing the data in the form ofmarks, the record carrier adhering to a pre-defined, standardizedcondition with respect to a physical parameter, characterized in thatthe record carrier comprises parameter information, which parameterinformation is of a higher precision than the precision of the physicalparameter mentioned in the pre-defined, standardized condition.
 2. Arecord carrier according to claim 1, characterized in that the parameterinformation is to be used for assisting writing a visible label on therecord carrier.
 3. A record carrier according to claim 1, characterizedin that the physical parameter is the track pitch of the record carrier.4. A record carrier according to claim 3, characterized in that theaverage track pitch, according to the pre-defined, standardizedcondition with respect to the track pitch, when expressed in micrometer,is expressed in two decimals, and that the information on the trackpitch stored on the record carrier, when expressed in micrometer, isindicated in at least three decimals.
 5. A record carrier according toclaim 4, characterized in that the record carrier is a DVD−RW disc or aDVD+RW disc, and the average track pitch is 0.74 μm.
 6. A record carrieraccording to claim 1, characterized in that the physical parameter isthe channel bit length.
 7. A record carrier according to claim 6,characterized in that the average channel bit length, according to thepre-defined, standardized condition with respect to the channel bitlength, when expressed in nanometer, is expressed in one decimal, andthat the information on the channel bit length stored on the recordcarrier, when expressed in nanometer, is indicated in at least twodecimals.
 8. A record carrier according to claim 7, characterized inthat the record carrier is a DVD−RW disc or a DVD+RW disc, and theaverage channel bit length is 133.3 nm.
 9. A record carrier according toclaim 1, characterized in that the physical parameter is the innerradius of the record carrier.
 10. A record carrier according to claim 9,characterized in that the inner radius, according to the pre-defined,standardized condition with respect to the inner radius, when expressedin millimeter, is expressed in one decimal, and that the information onthe inner radius stored on the record carrier, when expressed inmillimeter, is indicated in at least two decimals.
 11. A record carrieraccording to claim 10, characterized in that the record carrier is aDVD−RW disc or a DVD+RW disc, and the inner radius is 24.0 mm.
 12. Arecord carrier according to claim 1, characterized in that the patternof substantial parallel tracks exhibits a continuous sinusoidaldeviation of the track from the average centerline (6), a so-calledwobble (4.2), the parameter information being stored in the wobble. 13.A record carrier according to claim 1, characterized in that the patternof substantial parallel tracks comprises grooves and lands, the groovesbeing wobbled guidance tracks, the lands being the areas between thegrooves, the parameter information being stored in pits embossed on thelands, so-called pre-pits.
 14. A record carrier according to claim 1,characterized in that the parameter information is stored in apre-defined data field on the record carrier.
 15. A record carrieraccording to claim 1, characterized in that the record carrier comprisesa further area comprising an integrated circuit (7), the parameterinformation being stored in the integrated circuit.